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Anatomy and Function of the Heart Valves

What are heart valves?

The heart has 4 chambers, 2 upper chambers (atria) and 2 lower chambers (ventricles). Blood passes through a valve before leaving each chamber of the heart. The valves prevent the backward flow of blood. Valves are actually flaps (leaflets) that act as one-way inlets for blood coming into a ventricle and one-way outlets for blood leaving a ventricle. Normal valves have 3 flaps (leaflets), except the mitral valve. It only has 2 flaps. The 4 heart valves are:

• Tricuspid valve. This valve is located between the right atrium and the right ventricle.

• Pulmonary valve. The pulmonary valve is located between the right ventricle and the pulmonary artery.

• Mitral valve. This valve is located between the left atrium and the left ventricle. It has only 2 leaflets.

• Aortic valve. The aortic valve is located between the left ventricle and the aorta.

How do the heart valves work?

As the heart muscle contracts and relaxes, the valves open and shut. This lets blood flow into the ventricles and atria at alternate times. Here is a step-by-step description of how the valves work normally in the left ventricle:

• When the left ventricle relaxes, the aortic valve closes and the mitral valve opens. This lets blood flow from the left atrium into the left ventricle.

• The left atrium contracts. This lets even more blood to flow into the left ventricle.

• When the left ventricle contracts, the mitral valve closes and the aortic valve opens. This is so blood flows into the aorta and out to the rest of the body.

• While the left ventricle is relaxing, the right ventricle also relaxes. This causes the pulmonary valve to close and the tricuspid valve to open. This lets blood flow into the right ventricle that was returned to the right atrium from the body.

• When the left ventricle contracts, the right ventricle also contracts. This causes the pulmonary valve to open and the tricuspid valve to close. Blood flows out from the right ventricle to the lungs before it is returned to the left atrium as fresh, oxygenated blood.

What is heart valve disease?

Heart valves can have several problems. These include:

• Regurgitation is a leaky valve. This means the valve doesn't fully close, and the blood flows backward through the valve. This results in leakage of blood back into the atria from the ventricles in the case of the mitral and tricuspid valves. Or it leaks back into the ventricles in the case of the aortic and pulmonary valves. This can cause the chambers to be overworked because they have to pump the extra blood that was returned. Over time, this can cause structural and functional changes in the heart chambers. These changes prevent the chambers from pumping blood normally.

• Stenosis is a narrowed valve. With stenosis, the valve opening is narrowed, and the valve doesn't open correctly. This makes it harder for the heart to pump blood across the narrowed valve. The heart must use more force to pump blood through the stiff (stenotic) valve or valves. This can also cause structural and functional changes to the different chambers of the heart. These changes prevent the heart from pumping blood normally.

• Atresia. This means the valve opening doesn't develop normally during childhood. This prevents blood from passing from an atrium to a ventricle, or from a ventricle to the pulmonary artery or aorta. Blood must find another route. This is usually through a problem present at birth (congenital). This might be an atrial septal defect or a ventricular septal defect. This acts as another route for the blood to move through the heart

When heart valves fail to open and close correctly, the damage to the heart can be serious. The harm can affect the heart's ability to pump blood through the body.

Blood flow through the heart involves contractions of the heart muscle to move blood from the right chambers of the heart to the lungs&#;where it receives oxygen&#;and then to the left chambers of the heart where it is pumped to the rest of the body through a network of blood vessels.

Involved in this process are four heart valves that are synchronized to open and shut with each heartbeat. This ensures the consistent flow of blood in one direction from the heart via arteries (which carry oxygenated blood) and back to the heart via veins (which carry deoxygenated blood along with carbon dioxide).

This article maps the order of blood flow through the heart. It also describes problems that can affect blood flow when different parts of the circulatory system malfunction.

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Components of the Heart Involved in Blood Flow

The heart has two upper chambers, called the left and right atria, and two lower chambers, called the left and right ventricles. With each heartbeat, blood moves from one chamber to the next through a series of heart valves.

The heart rate and rhythm are controlled by the cardiac conduction system which delivers electric impulses that contract and relax the heart muscle.

Several major arteries and veins are involved in this process:

• The pulmonary artery transfers blood from the heart to the lungs.
• The pulmonary vein transfers blood from the lungs to the heart.
• The aorta delivers oxygenated blood from the heart to the rest of the body.
• The superior vena cava and inferior vena cava transport deoxygenated blood from the body back to the heart.

There are four valves that control blood flow in and out of the chambers of the heart:

• The tricuspid valve is located between the right atrium and the right ventricle.
• The pulmonary valve is located between the right ventricle and the pulmonary artery.
• The mitral valve is located between the left atrium and the left ventricle.
• The aortic valve is located between the left ventricle and the aorta.

Order of Blood Flow Through the Heart: Step by Step

Right Side of Heart

Here is the path that blood takes in the right side of the heart:

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1. The blood first enters the right atrium from the superior and inferior vena cava.
2. It then flows through the tricuspid valve into the right ventricle.
3. The blood then moves through the pulmonary valve into the pulmonary artery.
4. The pulmonary artery carries blood to the lungs where it takes up oxygen.

Left Side of Heart

Here is the path that blood takes in the left side of the heart:

1. Oxygenated blood returns to the heart through the pulmonary vein into the left atrium.
2. The blood then moves through the mitral valve into the left ventricle.
3. The left ventricle then pumps the blood through the aortic valve into the aorta.
4. From the aorta, the blood is transported through the network of blood vessels, delivering oxygen and nutrients to tissues and taking carbon dioxide and wastes from tissues.
5. Deoxygenated blood returns to the heart via the superior and inferior vena cava, and the cycle begins again.

Order of Blood Flow Through the Body: Step by Step

Once oxygenated blood leaves the heart, it is pumped through a network of vessels throughout the body to deliver nutrients and oxygen to cells.

Here is the path blood flows once it exits the left side of the heart:

1. Oxygenated blood from the left side of the heart gets pumped out of the aorta, the largest vessel of the body. The aorta extends from the left ventricle of the heart down into the abdomen.
2. Blood then flows through arteries that branch off from the aorta. These arteries deliver blood to different areas of the body.
3. Arteries then split into smaller vessels known as arterioles, which then carry blood to the smallest vessels in the body&#;the capillaries.
4. The capillaries deliver oxygen and nutrients to the tissues of your body and simultaneously remove carbon dioxide to be eliminated in the lungs.
5. Deoxygenated blood from the capillaries then flows back to the heart through small vessels known as venules.
6. The venules then gradually merge to form veins.
7. Blood enters back into the heart via large veins known as the superior and inferior vena cava.
8. Blood is then pumped through the right side of the heart, into the lungs to get oxygen, and back into the left side of the heart.

What Is the Correct Order of Blood Vessels From the Heart?

Oxygenated blood from the left side of the heart gets pumped out of the aorta. From there, blood flows through arteries, arterioles, and then capillaries (tiny blood vessels that transport blood, nutrients, and oxygen to cells).

Deoxygenated blood from the capillaries then flows back to the heart through venules, veins, and ultimately through the superior and inferior vena cava.

Role of Heart Valves With Blood Flow

The four heart valves prevent the backward flow of blood and keep blood moving in one direction. The valves are comprised of flaps of muscular tissues that open in one direction. The tricuspid, pulmonary, and aortic valves have three flaps, while the mitral valve has two flaps.

The tricuspid and mitral valves are located on each end of the two ventricles. They act as one-way inlets of blood on one side of a ventricle and one-way outlets of blood on the other side of a ventricle.

The pulmonary valve regulates the flow of blood in and out of the lungs, while the aortic valve regulates the flow of blood out of the heart and to the body.

The sound of your heartbeat is largely due to the opening and shutting of the valves. The low-pitched "lub" sound is due to the shutting of mitral and tricuspid valves, while the high-pitched "dub" sound is caused by the shutting of the aortic and pulmonary valves.

Conditions That Affect Normal Blood Flow

A healthy heart normally beats anywhere from 60 to 70 times per minute when you're at rest. This rate can be higher or lower depending on your general health and physical fitness. Athletes generally have a lower resting heart rate.

Your heart rate will increase when you move or engage in physical activity. This is because your muscles use oxygen while they work. In response, the heart works harder to bring oxygenated blood where it is needed.

Certain conditions can affect blood flow to and from the heart, including:

• Cardiac arrhythmia: This is a group of disorders that cause irregular heartbeats due to problems with electrical impulses.

  Atrial fibrillation

  is a common form of this.

• Heart blocks: These are problems with the cardiac conduction system, including atrioventricular (AV) block or an advanced bundle branch block.

• Heart valve disease: Damaged valves can leak and reduce the amount of blood delivered to tissues. The cause may be congenital (something you are born with), degenerative (in which a valve gradually wears out with age), or due to heart disease.
  Stenosis, a stiffening of the heart valve, also can disrupt blood flow.
• Heart failure: This is when the heart is unable to pump enough blood to meet the body's needs. The causes are many, including heart disease, lung disease, genetics, and infections.

• Cardiac ischemia: This is reduced blood flow due to a partially or fully obstructed blood vessel. One common cause of this is a heart attack.

Summary

Blood flow moves in one direction through the chambers of the heart. Electrical impulses are generated to make your heart beat. Heart valves open and shut to regulate blood flow. Cardiac arrhythmia, heart blocks, heart valve disease, heart failure, and cardiac ischemia can all affect the normal flow of blood to and from the heart.

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